Depth of field extension system and method

Abstract

The present invention relates to a system and method for extending a depth of field for an optical system, the system including a binary phase mask disposed between first and second lenses of the optical system, and a controller for controlling a binary phase structure formed on the phase shift mask.

Description

Technical Field

[0001] The present invention relates to a depth of field extension system and method, and more particularly, to a system and method for extending the depth of field (DOF) of an optical system using a binary phase structure.

Background Art

[0002] Optical systems are utilized for diagnosing the shape and condition of imaging targets in various industrial fields including the medical field. At this time, the optical system must satisfy the requirements for optical signal quality in order to provide an optical signal having sufficient resolution and accuracy for use.

[0003] In particular, defocus of an optical system is an element that can damage the optical signal quality. Therefore, a technique for extending (increasing) the depth of field (DOF) is required to solve such a defocus problem. In particular, a trade-off relationship occurs between depth and resolution in a non-interferometric optical system. That is, when the depth is extended (increased), a problem occurs in that the resolution decreases.

[0004] Therefore, there is a need for an improved solution that can overcome the trade-off relationship between depth and resolution to some extent while extending the depth of field.

[0005] However, the above-described content simply provides background information for the present invention and does not correspond to already published technologies.

Summary of the Invention

Problems to be Solved by the Invention

[0006] To solve the problems of the conventional technology described above, the present invention aims to provide a system and method for extending the depth of field (DOF) of an optical system using a binary phase structure.

[0007] However, the problems that this invention aims to solve are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those with ordinary skill in the art to which this invention pertains from the following description. [Means for solving the problem]

[0008] A system according to one embodiment of the present invention, which solves the above-mentioned problems, is a system for extending the depth of field of an optical system, and is disposed between the first and second lenses of the optical system. phase transition The system includes a mask and a control unit that controls the binary phase structure formed on the phase transition mask.

[0009] The control unit may, after evaluating the binary phase structure of the phase transition mask using the light output from the second lens, use the binary phase structure as is or modify it based on the results of the evaluation.

[0010] The phase transition mask may include first and second regions that perform different phase transition actions with respect to light.

[0011] The first region may emit the incident light with a first phase delay, and the second region may emit the incident light with a second phase delay.

[0012] The first region may emit the incident light with a phase delay of 0°, and the second region may emit the incident light with a phase delay of 180°.

[0013] Multiple first and second regions may be provided and formed alternately.

[0014] The second region may be located in the center.

[0015] The aforementioned phase transition The mask may be implemented by a spatial light modulator or a grating light valve.

[0016] The control unit can be modified to the optimal binary phase structure using particle swarm optimization.

[0017] A method according to one embodiment of the present invention is a method for extending the depth of field of an optical system, wherein between the first and second lenses of the optical system phase transition Transfer The process includes the steps of arranging a mask and applying an optimal binary phase structure while controlling the binary phase structure formed on the phase transition mask.

[0018] The application step may include evaluating the binary phase structure of the phase transition mask using the light output from the second lens, and then deciding whether to use the binary phase structure as is or to modify it based on the results of the evaluation.

[0019] The aforementioned application step may include the step of applying the optimal binary phase structure using particle swarm optimization. [Effects of the Invention]

[0020] The present invention, configured as described above, has the advantage of being able to extend the depth of field (DOF) of an optical system using a binary phase structure.

[0021] In addition, the present invention has the advantage of significantly reducing the parameters used for the design of a binary phase mask and optimizing the performance by generating an optimal binary phase structure based on particle swarm optimization (PSO).

[0022] The effects obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those with ordinary knowledge in the technical field to which the present invention pertains from the following description.

Brief Description of Drawings

[0023] [Figure 1] It is a schematic block diagram of a system (100) according to an embodiment of the present invention. [Figure 2] It is a diagram showing an example when the system (100) according to an embodiment of the present invention is applied to an optical system (101). [Figure 3] It is a diagram showing various examples of a binary phase structure in the plane of a phase transition mask (110). [Figure 4] It is a schematic block diagram of an electronic device (120). [Figure 5] It is a diagram showing an example when a point light source is incident on an optical system with or without the application of a phase transition mask (110). [Figure 6] It is a diagram showing an example when light from subjects at various distances is incident on an optical system with or without the application of a phase transition mask (110). [Figure 7] It is a flowchart showing a control method according to an embodiment of the present invention. [Figure 8] It is a diagram showing the concept of a control method according to an embodiment of the present invention. [Figure 9] It is a diagram showing the concept of a control method according to an embodiment of the present invention. [Figure 10] It is a diagram showing an overview of video acquisition using an optical system (101). [Figure 11]This figure shows the change in image quality and point diffusion function at different depths relative to the optical axis direction (u) of a typical optical system. [Figure 12] This figure shows various continuous phase patterns and the results obtained from the binary evolution of each pattern. [Figure 13] This figure shows the binary evolution result of a continuous phase pattern consisting of a quadratic expression formed by the combination of a linear term and a quadratic term. [Figure 14] This figure shows numerous binary phase structures and their focal results obtained by generating a continuous function by adjusting the coefficients of the linear and quadratic terms, and then binary-evolving the generated function. [Figure 15] This figure shows numerous binary topological structures generated using quadratic and quartic terms. [Modes for carrying out the invention]

[0024] The above-mentioned objectives, means, and effects of the present invention will become clearer from the following detailed description in conjunction with the accompanying drawings, so that a person with ordinary skill in the art to which the present invention belongs will be able to easily implement the technical idea of ​​the present invention. Furthermore, in describing the present invention, if it is judged that a specific description of prior art related to the present invention may obscure the gist of the present invention, such detailed description will be omitted.

[0025] The terms used herein are for illustrative purposes only and are not intended to limit the invention. In this specification, singular nouns may include plural nouns unless otherwise specified in the statement. In this specification, terms such as “includes,” “equip,” “possess,” or “have” do not exclude the presence or addition of one or more other components other than those mentioned.

[0026] In this specification, terms such as “or” and “at least one” can represent one of the words listed together or a combination of two or more words. For example, “A or B” and “at least one of A and B” may include only one of A or B, or both A and B.

[0027] In this specification, explanations using "for example" or similar phrases should not be limited to the various embodiments of the invention by effects such as tolerances, measurement errors, limits of measurement accuracy, and other commonly known factors, as the information presented may not be exactly the same as the cited characteristics, variables, or values.

[0028] In this specification, when one component is described as being “linked” or “connected” to another component, it should be understood that it may be directly linked or connected to that other component, but there may be other components in between. On the other hand, when one component is described as being “directly linked” or “directly connected” to another component, it should be understood that there are no other components in between.

[0029] In this specification, when one component is described as being "on top of" or "in contact with" another component, it should be understood that it may be directly in contact with or connected to the other component, but there may be other components in between. On the other hand, when one component is described as being "directly on top of" or "in contact with" another component, it should be understood that there are no other components in between. Other expressions describing the relationship between components, such as "between" and "directly between," can be interpreted in a similar manner.

[0030] In this specification, terms such as "first," "second," etc., may be used to describe various components, but the components should not be limited by these terms. Furthermore, these terms should not be interpreted as limiting the order of the components, but rather may be used to distinguish one component from another. For example, "first component" can be named "second component," and similarly, "second component" can be named "first component."

[0031] Unless otherwise specified, all terms used herein will be used in a sense that can be commonly understood by a person with ordinary skill in the art to which this invention pertains. Furthermore, terms defined in commonly used dictionaries will not be interpreted ideally or excessively unless explicitly defined otherwise.

[0032] A preferred embodiment of the present invention will be described in detail below with reference to the attached drawings.

[0033] Figure 1 is a schematic block diagram showing a system 100 according to one embodiment of the present invention, and Figure 2 is an example of applying the system 100 according to one embodiment of the present invention to an optical system 101.

[0034] System 100 according to one embodiment of the present invention is a system for extending the depth of field (DOF) of an optical system 101. In this system, the optical system 101 includes a number of lenses and performs various optical actions on the incident light source (for example, actions such as collecting and refracting the light source and creating an optical image on the object). For example, the optical system 101 may be an image capture device, but is not limited to this.

[0035] Such an optical system 101 includes a first lens 102 positioned close to the input portion into which light from a light source is incident, and a second lens 103 positioned close to the output portion into which light is finally emitted by optical action. For example, light from a light source may be incident from the front region of the first lens 102, and light may be emitted from the rear region of the second lens 103 positioned behind the first lens 102, and a focal point may be formed for the light emitted from the rear region.

[0036] Such a system 100 includes a phase shift mask 110 and an electronic device 120, as shown in Figures 1 and 2.

[0037] Figure 3 shows various examples of binary phase structures in the plane of the phase transition mask 110. In this case, the plane refers to the plane formed by axes (x and y axes) perpendicular to the optical axis (z axis).

[0038] The phase transition mask 110 is a mask that shifts the incident light in a binary phase manner, and may also be called a binary phase mask (BPM). It may be placed between the first and second lenses 102 and 103 of the optical system 101. That is, referring to Figure 2, the phase transition mask 110 includes a binary phase structure in the region through which light passes in its plane. In this case, the binary phase structure includes first and second regions 111 and 112, respectively, which perform different phase transition actions. As a result, the light passing between the first and second lenses 102 and 103 is delayed and emitted from the first and second regions 111 and 112 as being in different phases.

[0039] In other words, in the light-passing region of the plane of the phase transition mask 110, in at least one first region 111, the incident light can be delayed by a first phase (e.g., a phase of 0°) before being emitted, and in at least one other second region (e.g., the remaining region) 112, the incident light can be delayed by a second phase (e.g., a phase of 180°) before being emitted. In this case, the first and second regions 111 and 112 may be formed alternately one at a time.

[0040] As an example, referring to Figure 3, in the plane of the phase transition mask 110, the light-passing region is a circular region, and a circular second region 112 is located in the center of the light-passing region, and a circular band-shaped first region 111 may be located around the central second region 112. Of course, a circular band-shaped second region 112 may be located around the first region 111, and a circular band-shaped first region may be located around the circular band-shaped second region 112. 111Further arrangements may be made, and the first and second regions 111 and 112 may be arranged alternately. In addition, a third region 113, which blocks light, may be placed in the outermost region of the plane of the phase transition mask 110. Of course, the first and second regions 111 and 112 may be formed in the opposite pattern to that described above (i.e., a pattern in which the first region 111 is located in the center). The shape, number, and size of each region for the first region 111 and the second region 112 may be designed in various ways, and in particular, they may be designed by controlling the electronic device 120 described later.

[0041] The phase transition mask 110 is preferably a device that can dynamically adjust the shape, number, and size of each region for the first region 111 and the second region 112. As an example, the phase transition mask 110 can be implemented by a spatial light modulator (SLM) or a grating light valve (GLV). In the case of an SLM, the space of the first and second regions 111, 112 is formed by the input of an electrical or optical signal, and the phase of the incident light is changed in each of the first and second regions 111, 112 and output. Such an SLM may be a MEMS (Micro-Electro-Mechanical System) based SLM or an LC (Liquid Crystal) based SLM. In the case of a GLV, the first and second regions 111, 112 are formed by a dynamically adjustable diffraction grating, and the phase of the incident light is changed in each of the first and second regions 111, 112 and output.

[0042] Of course, in the case of a dynamically adjustable device such as an SLM or GLV, the phase transition mask 110 is connected to a phase structure control unit (not shown) that embodies its binary phase structure. Such a phase structure control unit may include a memory that stores information for embodying the binary phase structure of the phase transition mask 110, and a processor that processes the embodying of the binary phase structure using the information stored in the memory.

[0043] However, the present invention is not limited thereto, and the phase transition mask 110 may be constructed by using physical steps to realize the above-mentioned first and second regions 111 and 112 by methods such as imprinting, thin film deposition, wet / dry etching, or hologram film.

[0044] Figure 4 is a schematic block diagram of the electronic device 120.

[0045] The electronic device 120 is a computing-capable electronic device and may have at least a first and a second function. Specifically, the first function is to generate control signals for the binary phase structure of the phase transition mask 110 (i.e., the design of the shape, number, and size of each region for the first region 111 and the second region 112). The second function is to apply the current binary phase structure of the phase transition mask 110 to the optical system 101 and evaluate the current binary phase structure using the output final light. The first function is performed during initialization, and thereafter, the first function may be repeated so that the modified binary phase structure of the phase transition mask 110 is applied based on the evaluation results of the second function.

[0046] For example, the electronic device may be a general-purpose computing device such as a desktop personal computer, laptop personal computer, tablet personal computer, netbook computer, workstation, smartphone, smart pad, or mobile phone, or it may be a dedicated embedded system embodied based on Embedded Linux®, etc., but is not limited to these.

[0047] Referring to Figure 4, the electronic device 120 may include an input unit 121, a communication unit 122, a display 123, a memory 124, and a control unit 125.

[0048] The input unit 121 generates input data in response to various user inputs and may include various input means. For example, the input unit 121 may include, but is not limited to, a keyboard, keypad, dome switch, touch panel, touch key, touchpad, mouse, menu button, etc.

[0049] The communication unit 122 is configured to communicate with other devices such as the phase transition mask 110 or the phase structure control unit. For example, the communication unit 122 can transfer control information of the binary phase structure of the phase transition mask 110 generated by the first function to the phase transition mask 110 or its phase structure control unit. The communication unit 122 can also receive information necessary for the execution of the first and second functions from other terminals or servers. For example, the communication unit 122 can perform wireless communication such as 5G (5th generation communication), LTE-A (long term evolution-advanced), LTE (long term evolution), Bluetooth®, BLE (Bluetooth® low energy), NFC (near field communication), and Wi-Fi communication, or wired communication such as cable communication, but is not limited to these.

[0050] The display 123 displays various video data as a screen and may consist of a non-emissive panel or an emissive panel. For example, the display can display a screen showing the processing steps and results of the execution of the first and second functions. For example, the display may include, but is not limited to, a liquid crystal display (LCD), a light-emitting diode (LED) display, an organic light-emitting diode (OLED) display, a micro-electro-mechanical systems (MEMS) display, or an electronic paper display. The display may also be combined with the input unit 121 to be implemented as a touch screen or the like.

[0051] Memory 124 stores various information necessary for the operation of the electronic device 120. That is, memory 124 can store control program information and the like necessary for the execution of the first and second functions. For example, memory 124 may include, but is not limited to, hard disk type, magnetic media type, CD-ROM (compact disc read-only memory), optical media type, magneto-optical media type, multimedia card micro type, flash memory type, ROM type (read-only memory type), or RAM type (random access memory type), depending on its type. Also, memory 124 may be, but is not limited to, a cache, buffer, main memory, or auxiliary memory, depending on its use / location, or a separately provided storage system.

[0052] The control unit 125 can perform various control operations of the control device 120. Specifically, the control unit 125 can control the execution of the first and second functions, control the execution of the control program stored in the memory 124 and the control method described later, and control the operation of the remaining components of the electronic device 120, namely the input unit 121, the communication unit 122, the memory 124, the display, etc. For example, the control unit 125 may include, but is not limited to, at least one processor, which is hardware, and a process, which is software performed on that processor.

[0053] During the execution of the first function, the control unit 125 can control the design of the binary phase structure of the phase transition mask 110. That is, during initialization, the control unit 125 can derive the binary phase structure (initial binary phase structure) of the phase transition mask 110 arbitrarily or according to pre-set values. Subsequently, the phase structure control unit can derive a modified binary phase structure of the phase transition mask 110 based on the evaluation results obtained by executing the second function on the previously modified binary phase structure, using the particle swarm optimization (PSO) technique described later.

[0054] Of course, if necessary, the control unit 125 can also transmit control signals for the derived binary phase structure to the phase transition mask 110 or phase structure control unit located in the optical system 101. In this case, the phase transition mask 110 or phase structure control unit can reflect the binary phase structure based on the received control signals and realize the first region 111 and the second region 112.

[0055] Meanwhile, during the execution of the second function, the control unit 125 controls the measurement unit 131 to derive distance-specific focal shapes and image forms predicted by the current binary phase structure of the phase transition mask 110. Subsequently, the control unit 125 derives depth-specific image quality (e.g., structural similarity, peak signal-to-noise ratio, mean squared error, etc.) based on the prediction results and controls the evaluation of whether the given image quality conditions are met in the target depth range.

[0056] If the video quality conditions are not met as a result of the evaluation by performing this second function, the control unit 125 can perform the first function again on a PSO basis to derive a modified binary phase structure of the phase transition mask 110.

[0057] Figure 5 shows an example with and without the application of the phase transition mask 110 when a point light source is incident on the optical system, and Figure 6 shows an example with and without the application of the phase transition mask 110 when light from objects at various distances is incident on the optical system.

[0058] Referring to Figure 5, it can be seen that when the phase transition mask 110 is applied to the optical system 101, it is possible to control the focusing pattern for a point light source. That is, by applying the phase transition mask 110 to the optical system 101, 5 As shown in the figure below, it is possible to change the performance of the focus, and in particular, it is possible to increase the depth of field while keeping the size of the focus small. That is, by applying the phase transition mask 110 to the optical system 101, the depth of field can be extended.

[0059] Furthermore, referring to Figure 6, it can be seen that when the phase transition mask 110 is applied to the optical system 101, it is possible to control the depth of field. That is, by applying the phase transition mask 110 to the optical system 101, 6As shown in the figure below, it is possible to change the resolving power depending on the subject distance, and in particular, it is possible to image all subjects at different distances with good resolution. That is, by applying the phase transition mask 110 to the optical system 101, the depth of field can be extended.

[0060] The control method according to the present invention will be described in more detail below.

[0061] Figure 7 is a flowchart of a control method according to one embodiment of the present invention, and Figures 8 and 9 are conceptual diagrams showing a control method according to one embodiment of the present invention.

[0062] A control method according to one embodiment of the present invention (hereinafter referred to as "this control method") is performed by the control unit 125 of the system 100 described above, i.e., the electronic device 120. This control method is a method for designing a binary phase structure that has an optimally extended depth of field for the phase transition mask 110.

[0063] This control method may include a first step of placing a binary phase transition mask 110 between the first and second lenses 102 and 103 of the optical system, and a second step of applying an optimal binary phase structure while controlling the binary phase structure formed on the phase transition mask 110. As an example, as shown in Figure 7, this control method may include steps S201 to S204, which correspond to the detailed process of the second step.

[0064] First, in S201, the control unit 125 performs a first function, which is the step of deriving the design of the binary phase structure of the phase transition mask 110. At this time, during initialization, the design of the initial binary phase structure is derived either arbitrarily or according to pre-set parameters.

[0065] As an example, referring to Figures 3, 8, and 9, the phase transition mask 110 is set to a binary phase structure in which there are n first regions 111 and second regions 112 arranged alternately (where n is a natural number greater than or equal to 2), and the distance from its center point to the boundary of each first region 111 and second region 112 is ( A matrix having JPEG0007900792000001.jpg625) as an element. It can be set and used as JPEG0007900792000002.jpg535. In other words, the control unit 125 can design the phase transition mask 110 by processing the binary phase structure of the phase transition mask 110 as a variable.

[0066] Subsequently, in S202, the control unit 125 performs a second function and evaluates the design of the binary phase structure derived in S201. At this time, the control unit 125 can evaluate the binary phase structure of the derived phase transition mask 110 using the light output from the second lens 103. That is, the control unit 125 derives the distance-specific focal shape and image form predicted by the measurement unit 131 based on the current binary phase structure of the phase transition mask 110, and evaluates the depth-specific image quality based on the prediction results.

[0067] Subsequently, in S203, the control unit 125 checks whether the derived image quality result satisfies the given image quality conditions for the target depth range. If the conditions are met, the control unit 125 transmits a control signal for the current binary phase structure design to the phase transition mask 110 or the phase structure control unit (S204). As a result, the phase transition mask 110 or the phase structure control unit can realize the first region 111 and the second region 112 in accordance with the received control signal and the binary phase structure design.

[0068] If the conditions are not met in S203, S201 is repeated. In this case, the control unit 125 performs the first function based on particle swarm optimization (PSO) to derive a design for the modified binary phase structure of the phase transition mask 110 (i.e., the optimal previous phase structure). To this end, S202 and S203 may be repeated to evaluate the design for the modified binary phase structure and to confirm whether the conditions are met.

[0069] The process described above is repeated until the design of the binary phase structure satisfies the conditions. As an example, the initial binary phase structure is Set to JPEG0007900792000003.jpg89, the binary phase structure of the tth iteration is It may be set to JPEG0007900792000004.jpg89. That is, at the t-th time, If the evaluation result for JPEG0007900792000005.jpg89 does not meet the conditions, PSO will The modified binary phase structure of JPEG0007900792000006.jpg813 was derived, and The evaluation of JPEG0007900792000007.jpg813 may be conducted again.

[0070] The following describes the theory and principles applicable to the control method according to one embodiment of the present invention.

[0071] <Method and optical system for predicting focal shape and image form at different distances>

[0072] Figure 10 shows an overview of image acquisition using the optical system 101.

[0073] Referring to Figure 10, the general function of an optical device is to capture a portion of the light emitted or scattered from an object to create an image of that object. However, actual optical systems cannot capture all the light rays emitted from an object; they undergo diffraction and aberration due to refraction and distortion by lenses. The transfer function of such an optical system is known as the point spread function (PSF). The image creation method of an optical system using such a point spread function can be expressed as shown in equation (1) below, and the convolution of the object and the point spread function represents the image.

[0074]

number

[0075] The resolution (angular resolution, spatial resolution) is an index of the imaging ability of an imaging device, which means the ability to distinguish two objects separated from each other, and can be expressed by the shape of the point spread function.

[0076] FIG. 11 shows the point spread functions located at different depths with respect to the optical axis direction (u) of a general optical system and the change in image quality.

[0077] Referring to FIG. 11, as the light propagates from position a-a to position c-c, a change in the point spread function due to the diffraction of light occurs, and the resulting image distortion is inevitable. The depth of focus is defined as the section where the focus is maintained in the optical axis direction, and the depth of field is defined as the section of the field of view where the resolution at an acceptable level can be maintained.

[0078] <Details of applying PSO>

[0079] The optical system 101 includes the lens information of the optical system to which BPM is to be applied. Current optical design programs include Zemax, CodeV, LightTools, ASAP, TracePro, etc., and are based on "ray tracing" based on geometric optics. "Ray tracing" is performed by refraction by media having different refractive indices from each other and propagation occurring in one medium, and can be calculated based on the geometric information of the boundary of the medium and the optical physical properties of the medium. The calculated rays are analyzed using defined diffraction and physical optics calculation formulas, such as the modulation transfer function (MTF) and the point spread function (PSF).

[0080] In the present invention, the optical system 101 includes the same geometric information and optical physical properties of the lens as those of the imaging system for acquiring an actual image, and calculates the optical transfer function according to the depth of the subject.

[0081] - Video copying

[0082] Image reproduction is performed by convolution of the point diffusion function calculated by the optical system 101 and the test target. Test targets such as "USAF 1951," "Ronchi Ruling," and "Star," which are designed to help evaluate and correct the performance of the image system, may be used.

[0083] - Performance evaluation

[0084] Performance evaluation is performed by image quality assessment based on the depth of the subject. Referring to Table 1, two methods can be used for image quality assessment: a full-reference evaluation method that refers to distortion-free images, and a no-reference evaluation method that does not refer to distortion-free images.

[0085] [Table 1]

[0086]

number

[0087] Equation (2) is an equation for the cost (y) of this algorithm, and in this invention, a binary phase structure that minimizes this cost can be derived. In this case, f is the video quality evaluation result, f0 is the target video quality, JPEG0007900792000011.jpg89 is the binary topological structure matrix at the t-th iteration. JPEG0007900792000012.jpg917 represents the target depth expansion interval, and λ represents the regularization coefficient.

[0088] - PSO algorithm

[0089] In this invention, the PSO (particle swarm optimization) algorithm processes the binary phase structure for each t-th element. This was proposed to correct JPEG0007900792000013.jpg711. The PSO algorithm minimizes the cost (y) calculated by equation (2). JPEG0007900792000014.jpg76( This is an optimization algorithm for searching for JPEG0007900792000015.jpg714).

[0090] In the present invention, binary phase structure The cost (y) in JPEG0007900792000016.jpg76 is not a differentiable function, so minimum cost search using differentiation, such as gradient descent, is not possible. PSO is a methodology of mathematical optimization in which multiple particles (agents) exchange information with each other and simultaneously combine the stored information to find the optimal solution. Such swarm-based optimization has the advantage that, because each agent performs optimization while exchanging information with each other, even if one agent converges to a local optimum, the swarm can still converge to a global optimum.

[0091]

number

[0092]

number

[0093] The PSO algorithm optimizes one or more variable spaces using multiple agents, and equations (3) and (4) represent the velocity vector and position vector of the j-th agent for the i-th variable in t+1 iterations, respectively. Here, r1 and r2 are random numbers between 0 and 1, and c1 and c2 are coefficients for cognitive and social aspects, respectively. The agent best solution for information exchange between agents is a ij Therefore, the swarm lowest cost (global best solution) is The filename is JPEG0007900792000019.jpg812. The PSO algorithm is binary topological structure. To modify the JPEG0007900792000020.jpg89 design, the initial j-th agent may be expressed as the initial binary topological structure and equation (5).

[0094]

number

[0095] - PSO algorithm example

[0096] As an example, a binary phase filter for i components is a matrix It can be represented as JPEG0007900792000022.jpg836. The N binary phase filters processed in parallel by the agent are a matrix It can be represented as JPEG0007900792000023.jpg740. The initial N binary phase filters are a matrix. It can be expressed as JPEG0007900792000024.jpg741.

[0097] After t adjustments (iterations), the binary phase filter of the j-th agent is A solution like JPEG0007900792000025.jpg652 can be obtained, and the solution with the lowest cost among them is called the agent best solution, a ij It can be defined as follows.

[0098] global best solution, JPEG0007900792000026.jpg813 represents the best historical solution, showing the optimal result after t adjustments (iterations). The binary phase filter is a matrix after t adjustments. JPEG0007900792000027.jpg741; JPEG0007900792000028.jpg641;...; A solution like JPEG0007900792000029.jpg739 can be obtained, and among them, the solution with the lowest cost is the global best solution. It can be defined as JPEG0007900792000030.jpg813.

[0099] <Continuous Phase Pattern Binary>

[0100] In the present invention, the binary phase structure of the phase transition mask 110 can have a binary-evolved continuous phase pattern, and the specific patterning method is as follows.

[0101] Given a continuous phase pattern P(ρ) that is a function of the distance ρ from the center, its binary-evolved function can be expressed as shown in equation (6).

[0102]

number

[0103] Figure 12 shows various continuous phase patterns and the results obtained from the binary evolution of each pattern.

[0104] In other words, in Figure 12, (a1) is a continuous pattern represented by defocus aberration. It is represented as JPEG0007900792000032.jpg743 and expressed as a quadratic function of ρ with respect to the defocus parameter ψ. Also, in Figure 12, (a2) is the focal pattern that appears when (a1) is placed in front of the lens, and in each focal pattern diagram, the vertical direction is the direction of light propagation, and the point u=0 is the focal plane corresponding to the focal length. In this case, (a1) has the effect of moving the focal point along the direction of light propagation at the focal plane in proportion to the value of ψ. (b1) represents spherical aberration (SA), It is represented as JPEG0007900792000033.jpg636. Spherical aberration has the effect of elongating the focal point along the direction of propagation, as shown in (b2), and the degree of this effect increases with the gamma value.

[0105] In Figure 12, (c1) is an example of a linear function. Represented as JPEG0007900792000034.jpg740, this function exhibits the effect of increasing the length itself while simultaneously shifting the focus on the focal plane, as shown in (c2). The amount of shift and the degree of extension increase in proportion to the α value. The lower part of Figure 12 shows the results when each function in the upper part of Figure 12 is binarized using equation (6). The focus for each binarized function is morphologically similar to the focus generated by the continuous pattern, but generates additional symmetrical shapes around the focal plane. Using this phenomenon, polynomials with different degrees of ρ can be considered when generating continuous functions.

[0106] Figure 13 shows the binary evolution result of a continuous phase pattern consisting of a quadratic equation formed by the combination of a linear term and a quadratic term.

[0107] In Figure 13, (a) is a continuous phase pattern consisting only of linear equations. This is the result of binary evolution of JPEG0007900792000035.jpg740), where an α value of 5 was assumed. The resulting focal formation forms two extended foci symmetrically separated with respect to the focal plane, as shown in Figure 13(b). Figure 13(c) shows the continuous phase pattern expressed as a quadratic equation for ρ. This is the binary evolution result of JPEG0007900792000036.jpg861). The foci altered by this function show that two foci that were previously separated merge, as shown in Figure 13(d), resulting in an extended form compared to the existing foci.

[0108] Figure 13(e) shows the intensity graph at v=0 in Figures 13(b) and (d). It can be seen that the two foci, which were initially separated, merged as the ψ value increased, forming a single extended focus. In Figure 13, we only considered the case where the focus is extended using only first-order and second-order terms, but by using terms of various orders, it is possible to form foci with various shapes, and by adjusting the coefficient values ​​of each term, a large number of designs can be explored.

[0109] Figure 14 shows the coefficients of the linear and quadratic terms being adjusted ( JPEG0007900792000037.jpg965) A continuous function is generated, and the generated function is binary-evolved to obtain numerous binary phase structures and their focal results. Figure 15 shows the results using quadratic and quartic terms. JPEG0007900792000038.jpg868) shows the numerous binary phase structures generated.

[0110] As shown in Figures 14 and 15, by adjusting the coefficient values ​​of each term, the focus generation pattern can be predicted and a large number of binary phase structures can be found. In this embodiment, only first-order, second-order, and fourth-order terms were used, but when binary evolution is performed on polynomials that include terms of other orders, various binary phase structures can also be found.

[0111] As described above, the present invention has the advantage of being able to extend the depth of field (DOF) of an optical system using a binary phase structure. Furthermore, the present invention has the advantage of optimizing performance by generating an optimal binary phase structure based on particle swarm optimization (PSO), thereby significantly reducing the parameters used for designing the binary phase mask.

[0112] While specific embodiments have been described in the detailed description of the present invention, it goes without saying that various modifications are possible within the scope of the invention. Therefore, the scope of the present invention is not limited to the embodiments described, but should be defined by the claims described later and any claims equivalent thereto.

Claims

1. A system for extending the depth of field for an optical system, comprising a phase transition mask disposed between the first and second lenses of the optical system, The control unit controls the binary phase structure formed in the phase transition mask by performing the steps of: evaluating the quality of an image acquired by the optical system equipped with the phase transition mask; calculating a cost indicating the difference between the image quality and the target quality; and modifying the binary phase structure using a particle swarm optimization algorithm in a direction that minimizes the cost. The binary phase structure includes a first region and a second region that perform different phase transition actions with respect to light, The particle swarm optimization algorithm is a system that uses a matrix as a variable, the matrix having the distance from the center point of the binary phase structure to the boundary between the first and second regions as elements.

2. The system according to claim 1, wherein the first region delays the incident light by a first phase before emission, and the second region delays the incident light by a second phase before emission.

3. The system according to claim 1, wherein the first region emits incident light with a phase delay of 0°, and the second region emits incident light with a phase delay of 180°.

4. The system according to claim 3, wherein the first and second regions are provided in multiple quantities and are formed alternately.

5. The system according to claim 4, wherein the second region is located in the center.

6. The system according to claim 1, wherein the phase transition mask is embodied by a spatial light modulator or a grating light valve.

7. A method for extending the depth of field for an optical system, The steps include: placing a phase transition mask between the first and second lenses of the optical system; The steps include: applying the optimal binary phase structure while controlling the binary phase structure formed in the phase transition mask; Includes, The operation to control the binary phase structure is performed by evaluating the quality of the image acquired by the optical system equipped with the phase transition mask, calculating a cost representing the difference between the image quality and the target quality, and modifying the binary phase structure using a particle swarm optimization algorithm in a direction that minimizes the cost. The binary phase structure includes a first region and a second region that perform different phase transition actions with respect to light, The particle swarm optimization algorithm is a method that uses a matrix as a variable, the matrix having the distance from the center point of the binary phase structure to the boundary between the first region and the second region as elements.

8. The method according to claim 7, wherein the application step includes evaluating the binary phase structure using light output from the second lens based on the binary phase structure of the phase transition mask, and then deciding whether to use the binary phase structure as is or to change it based on the results of the evaluation.

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